I will be renting a car in Lagos and driving up to Porto. We plan to leave around 9 so we have plenty of time to stop somewhere along the way. We will have already spent 4 days in Lisbon so we have that area covered. If there is anywhere noteworthy that you think we should see I would appreciate any suggestions!
I prefer driving the N120 north, but you don’t have time to take this route, so you should take the less interesting E1 toll road. There are plenty of interesting places to stop between Lisbon and Porto such as Santarem, Alcobaca, Batalha and Coimbra. You could easily spend a week exploring this area.